The present invention relates to corresponding alignment mechanisms on both the package frame and the die to capture and align the optical fibers and/or lens with the optical micro-mechanical devices.
Fabricating complex micro-electro-mechanical systems (MEMS) and micro-optical-electro-mechanical systems (MOEMS) devices represents a significant advance in micro-mechanical device technology. Presently, micrometer-sized analogs of many macro-scale devices have been made, such as for example hinges, shutters, lenses, mirrors, switches, polarizing devices, and actuators. These devices can be fabricated, for example, using Multi-user MEMS Processing (MUMPs) available from Cronos Integrated Microsystems located at Research Triangle Park, North Carolina.
One method of forming a MEMS or MOEMS device involves patterning the device in appropriate locations on a substrate. As patterned, the device lies flat on top of the substrate. For example, the hinge plates of a hinge structure or a reflector device are both formed generally coplanar with the surface of the substrate using the MUMPs process. Applications of MEMS and MOEMS devices include, for example, data storage devices, laser scanners, printer heads, magnetic heads, micro-spectrometers, accelerometers, scanning-probe microscopes, near-field optical microscopes, optical scanners, optical modulators, micro-lenses, optical switches, and micro-robotics.
Packaging MEMS devices presents unique problems due to the physically active nature of the microstructures. To maintain a stable environment and to keep out dust particles, corrosive and/or potentially fouling vapors, etc., the micro-machined structures must be enclosed within a sealed package. A sealed package also minimizes the risk of physical damage during handling or operation. Traditional integrated circuit encapsulation methods such as epoxy resin potting and thermoplastic injection molding, while useful with integrated circuits, which have no moving parts, are incapable of use directly with micro-machined structures. The encapsulant must not contact the active portions of the micro-machined structure. Moreover, common encapsulation techniques such as injection molding, often requiring pressures of 1000 psi, would easily crush the microstructure.
One application for micro-machined structures is in connection with processing optical signals, such as optical switches, wavelength specific equalizers, polarization mode dispersion compensators, and the like. These applications, however, require coupling optical fibers with the packaged micro-machined structures. Various techniques are known for packaging MEMS devices, such as disclosed in U.S. Pat. No. 6,146,917 (Zhang et al.) EP0852337; and EP1057779. None of these packaging techniques, however, teach coupling optical fibers to the MEMS device.
The present invention relates to alignment mechanisms on both the packaged and the die containing the optical micro-mechanical devices. The alignment mechanism is adapted to receive and capture an optical interface, such as an optical fiber or optical lens. The package frame contains alignment mechanisms, such as V-grooves, that horizontally match with corresponding alignment mechanisms on the die. Vertically, the V-grooves are designed to align the centerline of the optical fibers and/or lenses to the active surface of the optical micro-mechanical devices.
In one embodiment, the package for optical micro-mechanical devices includes a die with one or more optical micro-mechanical devices on a first surface of a substrate. The first surface includes a die reference surface. One or more optical interconnect alignment mechanisms are formed in the first surface of the die. The optical interconnect alignment mechanisms are positioned to optically couple an optical interconnect with one or more of the optical micro-mechanical devices on the die. A package frame comprising an aperture and a package frame reference surface proximate the aperture is adapted to receive the die reference surface such that the optical micro-mechanical devices are located in the aperture. One or more optical interconnect alignment mechanisms are formed in the package frame. The optical interconnect alignment mechanisms on the package frame are positioned to align with corresponding optical interconnect alignment mechanisms on the die when the die reference surface is engaged with the package frame reference surface.
In one embodiment, distal ends of one or more optical interconnects are captured between in the optical interconnect alignment mechanisms on the package frame and the corresponding optical interconnect alignment mechanisms on the die when the die reference surface is engaged with the package frame reference surface.
The optical interconnect comprises one of an optical fiber, an optical lens or a combination thereof. The optical interconnect alignment mechanisms are typically V-grooves. The die reference surface and/or the package frame reference surface can be an optical interface reference plane.
One or more contact pads are typically interposed between the die reference surface and the package frame reference surface. The contact pads electrically couple one or more optical micro-mechanical devices with external electrical contacts. The contact pads can also electrically couple one or more optical micro-mechanical devices with a flexible circuit member. In one embodiment, the contact pads electrically couple one or more optical micro-mechanical devices with contact pads located on the package frame reference surface. In another embodiment, a flexible circuit extends across a rear surface of the die. One or more vias extend through the die and electrically couple the optical micro-mechanical devices to the flexible circuit.
In one embodiment, the die has a shoulder region adjacent to the optical micro-mechanical devices. Electrical traces extend from the optical micro-mechanical devices to the shoulder region. A flexible circuit coupled to the traces is located between the shoulder region and the optical interface reference plane.
In another embodiment, the package frame includes one or more alignment posts position to engage with the die reference surface. A cavity is provided adjacent to the alignment posts on a side opposite the aperture. A flexible circuit can extend through the cavity to electrically couple with contact pads on the die reference surface. An adhesive can be located in the cavity to retain the die to the alignment posts.
The aperture can be a rectangular shape or any other shape. A tooling fixture, such as a heat sink and/or tooling post are preferably located on the rear surface of the die. Alternatively, the tooling post is located on a rear surface of the die. An encapsulating material can be used to seal the die to the package frame. A cover seals the die to the package frame.
The present invention is also directed to an optical communication system including at least one packaged optical micro-mechanical device in accordance with the present invention.
The present invention is also directed to a method of packaging optical micro-mechanical devices. One or more optical interconnect alignment mechanisms are prepared on a die reference surface of the die. The optical interconnect alignment mechanisms are positioned to optically couple an optical interconnect with one or more optical micro-mechanical devices on the die. A package frame is prepared comprising an aperture and a package frame reference surface proximate the aperture adapted to receive the die reference surface such that the optical micro-mechanical devices are located in the aperture. One or more optical interconnect alignment mechanisms are prepared in the package frame. The optical interconnect alignment mechanisms on the package frame are positioned to align with corresponding optical interconnect alignment mechanisms on the die when the die reference surface is engaged with the package frame reference surface.
The method includes positioning one or more optical interconnects in the optical interconnect alignment mechanisms on the package frame and engaging the die reference surface with the package frame reference surface to capture the optical interconnects. One or more of the optical interconnects are captured between in the optical interconnect alignment mechanisms on the package frame and the corresponding optical interconnect alignment mechanisms on the die. In one embodiment, the die is sealed to the package frame using an encapsulating material. In another embodiment, a flexible circuit is electrically coupled to the die.